We are continuing our studies on the molecular basis of crown gall tumor formations on a number of fronts. We shall attempt to determine where the foreign DNA is located in the cell (nuclei, chloroplasts, mitochondria), and whether the DNA is integrated into one or many different sites. We shall compare a variety of cloned tumor lines in this respect. We shall determine whether plant protoplasts can take up, incorporate and express foreign DNA. Since Agrobacterium strains with usual host range have been isolated, we will compare their plasmids with other well-characterized plasmids of the same genus. Since A. rhizogenes is a close relative of A. tumefaciens, we shall determine if plasmid DNA is found in callus tissue derived from tissue derived from hairy root. We will isolate avirulent mutants of A. tumfaciens by insertion of the transposable elements Tn5 and Tn7 and define the site of insertion on the physical map of the plasmid. We will attempt to understand the basis of the avirulence in biochemical terms.